Brian Harner and Leo Sarli thought they were having just one or two people over to their cozy Columbia Pike offices a few months back, convening a small gathering of friends to discuss how to improve their South Arlington communities as Amazon.com Inc. (NASDAQ: AMZN) moves in.

Instead, 16 people showed up, eager to discuss how to handle the impending surge in growth for Crystal City and its surrounding neighborhoods.

“It really signaled to us that there was a real thirst for this type of process,” said Sarli, an architect with Harner at LAB Inc.

From those unexpected beginnings, Harner and Sarli would go on to help facilitate a very unusual set of community discussions, designed to connect residents directly with the developers re-shaping their neighborhoods.

The civic associations in the three communities closest to Amazon’s new headquarters — Crystal City, Arlington Ridge and Aurora Highlands — had watched closely as Arlington officials courted the tech giant, and many welcomed the news that Amazon would bring 25,000 employees to their backyards. But they feared what the spate of new development would mean for existing residents and, crucially, they harbored doubts that the county could mitigate any negative impacts.